There are many applications where it is necessary to perform various types of experiments that require that an object, or objects, be kept very stable for an extended period of time. To meet this need, specialized tables and clamps have been developed. A common way of holding an object is to clamp it to a horizontal surface such as an optical bench, a laboratory bench, or other type of bench. Commonly, these benches have various channels and threaded holes for mounting clamps and other mounting devices.
For many applications, the object under study must be mounted at a height above the bench. For example, testing of optical systems requires light to pass through the object without interference by the testing apparatus. To meet this requirement, various posts and spacers have been developed. As generally discussed in U.S. Pat. No. 5,039,043, posts and post holder arrangements have been used for precisely positioning optical components on an optical test table. Optical components, such as lenses, mirrors and lasers, must be precisely oriented with respect to each other in height and angular orientation. Typically, the optical components are held in a holder and mounted on a post and post holder arrangement.
FIG. 1 shows a post and post holder as it would appear on an optical table or breadboard. The optical table 10 is a rigid table which bears an array of threaded holes 12 on its surface. An optical component, such as a lens 14, is held in a holder having a threaded end 18, 16 which is in turn threaded onto a post 20 having a threaded end 21 held in a post holder 22. The post holder 22 is attached to the table via the threaded holes 12. Generally, such a post 20 and post holder 22 arrangement provides two degrees of freedom, vertical and rotational, about the axis of the post holder.
In order to move the optical component, the post 20 may be raised or lowered, or rotated about the axis of the post holder 22. The post is locked into place using a screw 24 inserted through the post holder 22 to contact the post 20, thereby frictionally holding the post 20 in place. The post holder 22 can generally be screwed directly into the threaded holes 12 in the bench 10, thus providing both an attachment to the bench 10 and vertical support for the object involved in the experiment.
Other current devices are found in the biological field. For example, when doing in vitro fertilization or other procedures where micron scale mechanical precision is required, various jigs or fixtures have been used. However, these devices have tended to be of the "jury-rigged" variety, and lack mechanical soundness.
A drawback of the mounting system illustrated by FIG. 1 is that it is relatively inflexible once it is placed on the bench. For example, the post 20, holder 16 and lens 14 can only be rotated about the post holder 22 axis or moved vertically with respect to the bench 10. Moving the lens 14 horizontally (e.g., to another threaded hole 12) requires disassembly of the post 20 and post holder 22, movement of the post holder 22, and reassembly of the post 20 and post holder 22. Such movement is less than optimal for the following reasons.
First, it is time consuming to disassemble and reassemble the device--especially where this must be done repeatedly. Second, many times the bench can become crowded, making it difficult to access the post 20 and post holder 22. Third, when loosening the screw 24, it is possible for the post 20 to suddenly slip downward when the screw is withdrawn sufficiently. This problem is addressed in the above-mentioned U.S. Pat. No. 5,039,043.
Apart from the time and access problems noted above, the illustrated system suffers performance deficiencies. First, the screw can scratch or score the post 20, making it necessary to replace the post 20. Second, the system can lead to accuracy problems due to even minor changes in location of the lens due to tightening the screw 24, which can skew the post 20 to one side of the post holder 22.
The biological mounting arrangements are further deficient because the object under operation is typically located in front of the holder. Since the object is adjacent the fixture, access to the fixture is limited, especially where modification requires access to the portion of the fixture adjacent the object.